robots.txt editor won’t save changes

I am trying to add a new rule using the Robots.txt editor to allow Twitter to access images when sharing. It shows in the preview correctly (see below) but after saving the changes, it reverts back to the default robots.txt.

Can you advise?

Thanks,

-Peter

User-agent: *

Allow: /wp-admin/admin-ajax.php

Disallow: /wp-admin/

User-agent: Twitterbot

Allow: /culturalpropertynews.org/

Sitemap: https://culturalpropertynews.org/sitemap.xml

Sitemap: https://culturalpropertynews.org/sitemap.rss

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